The present invention relates to an apparatus for fabricating semiconductor devices and, particularly, to such apparatus suitable to use in forming thin membranes on main surfaces of semiconductor substrates.
A lateral type reactor such as shown in FIG. 1 has been used heretofore as such apparatus. The lateral type reactor comprises a cylindrical tube 1 into which a plurality of semiconductor substrates 2 arranged vertically on a board 3 are inserted and various thin membranes are formed on the substrates 2 by means of reactions between them and various gases introduced through a gas port 4 thereinto sequentially.
For some reactions which need an electric field, a parallel flat type reactor such as shown in FIG. 2 has been also used. The latter type reactor comprises a reaction tube 1a in which at least a pair of parallel upper and lower electrodes 5a and 5b are arranged and, by means of reaction gases introduced thereinto through a gas port 4a, desired thin membranes are formed on surfaces of semiconductor substrates 2 disposed on the lower electrode 5b acting as a susceptor. In FIGS. 1 and 2, reference numerals 6 and 6a depict evacuation ports, respectively.
In any of these conventional apparata, the reaction tube has to be opened to atmosphere when the substrates are to be inserted into or removed from the tube. Thermal energy required in either apparatus to treat the semiconductor substrates therein is supplied by an external resistance heater, internal infrared lamp or RF induction heater etc. as disclosed in Japanese Patent Publication No. 24467/1986.
In such conventional apparatus, when the thickness of membrane to be formed is small, a control of membrane thickness becomes difficult due to the fact that undesired oxide membrane may be formed additionally during the semiconductor substrates are inserted into or derived from the apparatus. Further, problems of degradation of quality of formed membranes may occur due to oxidation thereof when the semiconductor substrates having the membranes are inserted into or removed from a reactor kept at high temperature.
Japanese Patent Publication No. 21025/1983 discloses a vertical cylinder type reactor in which semiconductor substrates are stacked on a carrier with suitable space therebetween and main surfaces thereof being down, to thereby make thicknesses of epitacially deposited membranes thereon uniform while preventing accumulation of dust thereon.
The latter reactor is, however, disadvantageous in that the semiconductor substrates must be supported with the main surfaces being down, which necessitates a relatively complicated supporting structure. In addition, the problems of thickness control and the degradation of membrane quality are not solved.